As one of the main environmental factors, low temperature is limiting for crop production. Chilling injury (CI) is a stress caused by low, non-freezing temperatures (0 to 12 °C) (Dong et al., 2019). Temperatures below 10 °C may injure tropical and subtropical crops, such as species of the Cucurbitaceae (Raison, 1974). Although some plants can withstand cold stress, low temperatures during the production of most summer vegetables such as cucurbits can cause reduced growth, leaf yellowing, and foliar necrosis.
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is an economically important cucurbit species belonging to the family Cucurbitaceae. It is cultivated throughout the world and total production is more than 118 million t (FAO, 2017). Grafting of watermelon is an established production practice that contributes resistance to soilborne diseases or tolerance to abiotic stresses (Bertucci et al., 2018). Watermelons are grafted to increase fruit and seed yield and plant growth by enhancing water and plant nutrient uptake (Kombo and Sari, 2019; Oda, 1995; Yetisir and Sari, 2003). The most common rootstocks for watermelon grafting are Cucurbita interspecific hybrids (C. moschata × C. maxima), the bottle gourd (Lagenaria siceraria) accessions that are highly resistant to soilborne fungi (Liu et al., 2015) and wild watermelon (C. amarus) (King et al., 2010; Kombo and Sari, 2019; Kong et al., 2014),
Chilling tolerance has been studied in cucumber (Chung et al., 2003; Kozik et al., 2007; Kozik and Wehner, 2008; Smeets and Wehner, 1997), watermelon (Ghanbari et al., 2018; Kozik and Wehner, 2014; Spalholz and Kubota, 2017), and melon (Diao et al., 2019; Li, 2012; Zhang et al., 2017); however, few studies have been done on bottle gourds (Ko et al., 2006; Liu et al., 2003; Xing et al., 2017), and Lagenaria genetic resources have not been screened for low temperature conditions.
A method for screening seedlings of cucumber for chilling tolerance was developed by Smeets and Wehner (1997) using controlled environmental conditions and cultigens that were tolerant (AR75-79, ‘Chipper’, ‘Pixie’, and ‘Wisconsin SMR 18’) or susceptible (Gy14, ‘Marketmore 76’, NCSU M28, NCSU M29, and ‘Poinsett 76’). Researchers concluded that genetic variation for chilling damage was greater at the first true leaf than at the cotyledon stage. Kozik and Wehner (2014) used a similar method for screening of watermelons. They tested 16 watermelon cultigens using four chilling durations (6, 12, 24, or 36 h) and 2 chilling temperatures (2 or 4 °C). They found 36 h at 4 °C or 24 h at 2 °C as optimal conditions for chilling treatment; PI 244018 was the most tolerant cultigen and NH Midget and Golden were the most susceptible cultigens.
USDA–Agricultural Research Service, Plant Genetic Resources and Conservation Unit in Griffin, GA (http://www.ars-grin.gov) has more than 235 PIs of Lagenaria siceraria (Levi et al., 2009). In this study, 163 Lagenaria accessions in USDA were evaluated for tolerance to low temperature.
Bertucci, M.B., Suchoff, D.H., Jennings, K.M., Monks, D.W., Gunter, C.C., Schultheis, J.R. & Louws, F.J. 2018 Comparison of root system morphology of Cucurbit rootstocks for use in watermelon grafting HortTechnology 28 629 636
Chung, S.M., Staub, J.E. & Fazio, G. 2003 Inheritance of chilling injury: A maternally inherited trait in cucumber J. Amer. Soc. Hort. Sci. 128 526 530
Diao, Q.N., Tian, S.B., Chen, Y.Y., Xiong, H.N. & Zhang, Y.P. 2019 Response of endogenous nitric oxide and sucrose metabolizing to chilling stress in melon seedlings Acta Botanica Boreali-Occident. Sinica 39 3 1551 1557
Dong, Z., Men, Y., Li, Z., Zou, Q. & Ji, J. 2019 Chlorophyll fluorescence imaging as a tool for analyzing the effects of chilling injury of tomato seedlings Scientia Hort. 246 490 497
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Ghanbari, F., Fatahi, S., Mohammadi, M. & Shayan, A.A. 2018 Improvement of tolerance to chilling in watermelon seedlings with methyl jasmonate and methyl salicylate Thai J. Agr. Sci. 51 1 1551 1557
King, S.R., Davis, A.R., Zhang, X.P. & Crosby, K. 2010 Genetics, breeding and selection of rootstocks for Solanaceae and Cucurbitaceae Scientia Hort. 127 106 111
Kong, Q.S., Chen, J.L., Liu, Y., Ma, Y.H., Liu, P., Wu, S.Y. & Bie, Z.L. 2014 Genetic diversity of Cucurbita rootstock germplasm as assessed using simple sequence repeat markers Scientia Hort. 175 150 155
Ko, B.R., Kwon, S.W., Jaskani, M.J. & Choi, J.S. 2006 Fatty acid composition and fad3 gene expression in roots of watermelon and gourd under low temperature Acta Hort. 710 377 382
Kozik, E.U., Klosinska, U. & Wehner, T.C. 2007 New sources of chilling resistance in cucumber, p. 227–232. In: P. Nowaczyk (ed.). Spontaneous and induced variation for the genetic improvement of horticultural crops. University Press, University of Technology and Life Sciences, Bydgoszcz, Poland
Levi, A., Thies, J., Ling, K.S., Simmons, A.M., Kousik, C. & Hassell, R. 2009 Genetic diversity among Lagenaria siceraria accessions containing resistance to root-knot nematodes, whiteflies, ZYMV or powdery mildew Plant Genet. Resour. 7 3 1551 1557
Li, J. 2012 Effects of chilling and low light on vegetative and physiological parameters of melon seedlings J. Henan Agricultural Sci. 41 5 1551 1557
Liu, H.Y., Zhu, Z.J., Lu, G.H. & Qian, Q.Q. 2003 Chilling tolerance and physiological parameters as influenced by grafting in watermelon seedlings Agr. Sci. China 2 10 1551 1557
Liu, B., Ren, J., Zhang, Y., An, J., Chen, M., Chen, H., Xu, C. & Ren, H. 2015 A new grafted rootstock against root-knot nematode for cucumber, melon, and watermelon Agron. Sustain. Dev. 35 251 259
Spalholz, H. & Kubota, C. 2017 Rootstock affected in-and poststorage performance of grafted watermelon seedlings at low temperature HortTechnology 27 93 98
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Xing, N.L., Zhang, H.B., Wang, Y.E., Huang, Y.P. & Wang, Y.H. 2017 Analysis of indexes for identification of tolerance of bottle gourd rootstock seedlings to low temperature and poor light Acta Agr. Jiangxi 29 9 1551 1557
Zhang, Y.P., Yao, X.Q., Yang, S.J., Xu, S. & Chen, Y.Y. 2017 Effects of low temperature treatment and recovery on the photosynthesis and antioxidant characteristics in melon seedlings Acta Agr. Shanghai 33 1 1551 1557